The present invention relates generally to fluid handling machines and, more particularly, to vane-type fluid displacement units having features of improved design.
Vane-type fluid displacement units are well known in the art. One such example of a typical vane pump is disclosed in U.S. Pat. No. 6,503,064 to Croke et al., which discloses a rotor having smooth top and bottom surfaces. Typically, the top and bottom surfaces of rotors are ground smooth to a surface finish of Ra 4-20 micro inches. Because of the ground surfaces of the rotor, fluid passing through the vane pump exerts a shear force on the rotor, thereby requiring greater input torque.
U.S. Pat. No. 5,560,741 to Edwards discloses a vane pump having a rotor with a trepanned or recessed portion centrally located on the top and bottom surfaces. The purpose of this recessed portion is to provide undervane fluid an escape path as the vanes move radially inward during rotation of the rotor and has no bearing upon the shear force exerted by the fluid on the rotor. Accordingly, there is a need in the art for an improved rotor that reduces the shear force exerted by the fluid on the top and bottom surfaces of the rotor.
It is therefore a principal object of the present invention to provide an improved vane-type displacement unit that operates with a minimum amount of input torque.
A further object of the present invention is to provide an improved rotor for a vane-type displacement unit that reduces the amount of shear force exerted by the fluid passing therethrough.
These and other objects will be apparent to those skilled in the art.